Chamber structure for guns



' P 1960 K. w. MAIER ETAL 2,952,089

CHAMBER STRUCTURE FOR GUNS Filed Jan. 16, 1957 2 Sheets-Sheet 1 2% CLEARANCE FIG-2 SAFETY zoo zoo FACTOR SAFETY FACTOR INVENTOR.

KARL W. MAIER JOHN L. WILSON fi gg sept- 1950 K. w. MAIER ETAL 2,952,089

CHAMBER STRUCTURE FOR GUNS Filed Jan. 16, 1957 2 Sheets-Sheet 2 1 ,9 fill/Z/ZZ/ ll l/l y 3/ W I \r A illll/lllllll fl s FIG-6 INVEN TOR. KARL W. MAIER JOHN L.W|LSON United States Patent CHAMBER STRUCTURE FOR GUNS Karl W. Maier, Cheshire, and John L. Wilson, Madison, Conn., assignors to Olin- Mathieson Chemical Corporation, a corporation of Virginia Filed Jan. 16, 1957, Ser. No. 634,443

2 Claims. (Cl. 42-76) This invention relates to pressure vessels and in particular to pressure vessels fabricated compositely of metallic materials and reinforced plastic materials.

Recently it has been recognized that the size and weight of metal structures, particularly those utilizing. steel, can be substantially reduced while safety factors It is a particular feature of the present invention to.

provide a firearm or ammunition component such as a gun chamber or a cartridge case where the component.

is composed of a layer of GRP and is radially spaced from an outer casing or jacket of steel or the like.

The general theory of the present invention hinges.

upon the realization that the theoretical yield strength of unidirectional GRP is approximately 250,000 psi; which, for purposes of comparison, represents about twice the yield strength of steel.

The chief advantage in arranging the GRP in such a manner that its wall is radially spaced from an exterior jacket is to permit the utilization of the superior strength of the glass fiber before transmitting a bursting load to the weaker outer metallic casing.

Accordingly, it is a particular object of the present invention to provide a new and improved firearm structure.

It is a further object of the invention to provide a laminate composed of metal and GRP having size and weight characteristics which are substantially less than the corresponding characteristics of a similar vessel fabricated entirely of steel.

A further object of the present invention is the provision of a composite metallic and GRP wall structure capable of withstanding bursting loads in excess of similar stresses if applied to an all-metallic structure of corresponding dimensions and configuration.

A further object of the present invention is the provision of a firearm chamber having a predetermined diameter ratio which, when subjected to hoop stresses of the order of 180,000 p.s.i., exhibits a greater factor of safety than would be available in an all-steel chamber having a comparable diameter ratio.

A chamber structure illustrating certain features of the invention may include a cylindrical vessel formed of an inner layer of glass reinforced plastic and a steel jacket surrounding the plastic structure, said steel jacket being radially spaced from the exterior surface of the plastic structure, and means for enclosing the ends of the vessel whereby it may be pressurized.

Although the principles of the present invention will be described in connection with several graphs superim posed upon sectional views of a pressure vessel embodying the invention, it is clear that the invention will have application wherever one is desirous of accomplishing the particular objects set out above.

The invention will be specifically described in connection with its adaptation to firearms with emphasis on its use in devising a new and improved chamber structure for a firearm and in connection with a new and improved cartridge case.

As stated before, it is not intended that the principles of the present invention be limited to the particula r examples hereinafter described; the examples have been selected primarily for the purpose of presenting exemplary arrangements thereof.

A more complete understanding of the invention may be obtained from the following detailed description thereof when read in conjunction with the appended drawings in which:

Fig. 1 is a cross sectional view of a pressure vessel composed entirely of steel;

Fig. 2 is a corresponding view of a pressure vessel embodying the principles of the present invention showing an inner chamber of GRP radially spaced [from an exterior steel jacket;

Fig. 3 is similar to Fig. 2 and shows graphically the relationship of the elements of the wall structure when the GRP tube has been stressed to the point of transmitting the load to the outer jacket;

Fig. 4 is a similar view showing the distribution of hoop stresses at the instant of application of the maximum bursting load upon the structure of Fig. 2;

Fig. 5 is a vertical section of a portion of a firearm showing to advantage the chamber structure thereof embodying the present invention and;

Fig. 6 is a view similar to Fig. 5 showing a cartridge casing which, in cooperation with the radially spaced interior wall of a chamber, embraces the principles of the present invention.

Referring now in detail to Fig. 1, there is shown a cross sectional view of steel tube 10. For purposes of this explanation of the invention, the sectional view of Fig. 1 may be considered to have been taken through a steel cylindrical pressure vessel. The ordinate of the graph represents the tangential or hoop stress set up in the wall of the cylinder as a result of a predetermined bursting pressure uniformly distributed about the interior of the vessel. The hoop stress is denoted in thousand pound per square inch units and is plotted against wall thickness assuming a 60,000 psi. internal pressure. In fact, the ordinates of Figs. 3 and 4 are also sealed in units of one thousand pounds per square inch. It is noted that the hoop stress falls off incrementally as the load is transmitted from the inner surface to the exterior surface of the cylinder. For purposes of this explanation, it may be assumed that the internal pressure applied to the cylinder of Fig. l is 60,000 psi. and that the diameter ratio (designated by the letter U) of the vessel is represented by the ratio of the outer diameter to the inner diameter. This ratio is 1.75 for the structure of Fig. 1.

In comparison, a reference to Fig. 2 discloses an inner GRP tube 11 and an outer steel jacket 12, each having a diameter ratio equal to 1.25, with an initial radial clearance of 2 percent (of the inner radius of the plastic tube) making a total diameter ratio of 1.59. These diameter ratios are not limiting and are supplied merely for purposes of comparison.

In the structure of Fig. 1 and with the application of 60,000 psi. internal pressure, a maximum hoop stress of the order of 120,000 p.s.i. is developed in the wall of the chamber which upon repeated application of init al pressure would result in yielding or the occurrence of a permanent set in the steel (because the value is in excess of the yield strength of steel). In prior art devices, the danger ofexceeding the yield strengthrof steelwas overcome, in the manufacture of gun barre1s,.-for example,

by building a two-piece wall structure where an outer steel jacket was shrunk over an inner steel liner in order the inner liner, reducing it-to zero, and then inject a: tensile stress in the inner liner and ultlmately transmit. a

substantial portion of the developed expansive forceto the outer jacket.

In contrast, a wall structure in accordance withvthc showing of Fig. 2 may be stressed readily by an internal gas .pressure of as much as 60,000 psi. without approaching the yield strength of the outer: steel jacket. This can best be shown by a reference to Figs. 3 and 4.wherein the hoop stresses corresponding to internal pressures of 35,000-p.s.i. and 60,000 psi. respectively are shown graphically. internal pressure represents the load at whichthe hoop stress set up in the GRP tube is at: the point of being transferred to the steel jacket.

In further referring. to Fig. 3, it is noted that the 35,000 p.s.i. internal pressure has expanded the GRP tube:

until it has taken up the 2 percent radial clearance and the outer diameter thereof now coincides with the internal diameter of the steel tube. The hoop stress in the; interior tube ranges from approximately 160,000 down to 125,000 with substantially no stress in the outer jacket.

A reference to Fig. 4 shows that as the internal pressure increases to 60,000 p.s.i., the hoopstress in the plastic tube increases to approximately 180,000 p.s.i.. while the hoop stress in the steel tube is of the order of 68,000 p.s.i. Since the maximum yield strength of the glass fibers is of the order of 250,000 p.s.i. and themaximum yield strength of the steel is of the order of 100,000 p.s.i., it is readily apparent that there is no danger of exceeding the respective yield strengths of the two materials. In fact, a very appreciable safety factor is apparent.

Referring now to Fig. 5, there is showna portion of the chamber of a firearm indicated generally by the reference numeral 13. The chamber is formed with a bore 14 having a tapered portion 16, a straight portion 17 and a final taper 18. Radially spaced from the bore 14 and supported at the left end in a counter bore 19 and at the forward end by a counter bore 21 is a metallic bushing 22 having a flange 23 which complements the counter bore 19. The bushing is formed with a jacket of GRP having an exterior configuration generally complementary to the interior configuration of the chamber. The exterior surface of the GRP tube is radially spaced from the interior,

combined walls 24 and 25. It is to be understood that the bushing 22 functions primarily as a means for positioning the GRP jacket with respect to the chamber.

In the examples shown a 35,000 pound,

Fig. 6 is a view similar to Fig. 5 and shows the present invention adapted to a shell casing or a cartridge casing wherein a brass or other metallic cartridge 26 is provided with a GRP tube 27 which is in turn radially spaced from a chamber structure 28. The head of the casing maintains the annular spacing by the engagement of the rim with a corresponding counter bore as at 29. The annular spacing is maintained in the forward end by theengagement of the rim with a corresponding counter bore as at 29. The annular spacing is maintained in the forward end by the engagement of the cartridge casing with the rifle barrel as at 31.

In both Figs. Sand 6 the walls of the chamber structures 24 and 28 respectively are of substantially less thickness and less weight than would be the case if the chambers were composed entirely of steel having adequate safety factors.

In Fig. 5, by utilizing the bushing 22 as a spacer for the GRP jacket and in Fig. 6, by utilizing the element 26 as a combined spacer andrcartridge case encircled by a GRP jacket, there have been devised two exemplary devices which utilize the principles of the present invention.

It is to be understood that various other arrangements and modifications, of the wall structure of the present invention may be undertaken without departing from the spirit .and scope thereof.

What is claimed is:.

1., Ina firearm a cylindrical chamber structure which is subject to internal pressure of the order of 60,000 p.s.i. comprising a rupturable metallic wall having a yield strength of. about 100,000 p.s.i., a bushing disposed in said.

chamber. and radially spaced from the internal surface of the wall, a glass fiber reinforced plastic jacket having a yield strength of about 250,000 p.s.i. carried by said bushing and spaced from the interior surface of the wallso as to provide an, annular void between the wall and the jacket,.said void extending along substantially the full length of the jacket, said radial spacing being about 2% of the inner radius of the jacket so that the wall and the jacket are free to elongate under said 60,000 p.s.i. pressure without exceeding the respectiveyield strengths.

2. A chamber structure as described in claim 1 wherein the diameter ratios of the metallic wall and the jacket, respectively, are about 1.25 and the total diameter ratio of the composite wall and jacket including the intervening radial spacingis about 1.61.

References Cited in the file of this patent UNITED STATES PATENTS 40,978 Crispin Dec. 15, 1863 181,977 Pieri Sept. 5, 1875 2,564,695 Johnson et al Aug. 21, 1951 2,736,117 Clarkson et al. Feb. 28, 1956 2,744,043 Ramberg May 1, 1956 2,774,283 Harvey Dec. 18, 1956 2,809,762. Cardona Oct. 15, 1957 2,847,786 Hartley et a1. Aug. 19, 1958 FOREIGN PATENTS 7,071 Great Britain 1894 212,862 Germany Aug. 11, 1909 324,424 Germany Aug. 27, 1920 

